1 February 2008
Human premotor cortex: anatomical and functional specialisations
Dr Hadwen Trust grantholders Tim Behrens and Heidi Johansen-Berg have used diffusion-weighted imaging tractography to examine the connectivity of the precentral cortex in vivo in human volunteers.
Compared to knowledge of the macaque brain (obtained from invasive tract-tracing experiments), less is known about the structural organisation of the human lateral premotor cortex. For example, information was lacking on whether this area is divided structurally and functionally into dorsal and ventral subregions, and how it relates to specific parietal and pre-frontal anatomical networks.
With the aid of a three-year grant from the Dr Hadwen Trust, the team at Oxford used multiple-fibre diffusion tractography to examine these connectivities in volunteers. Tractography is a relatively new, non-invasive approach that allows quantification of long-range connectivity in the human brain. The anatomy of fibrous tracts in the brain both reflects and shapes regional functional organisation, so connectivity patterns provide information about functionally distinct areas.
The team was successful in using tractography even in brain regions of fibre crossing and complexity. The research shows that there are indeed dorsal and ventral subregions in the human lateral premotor cortex, reproducibly distinguishable with tractography on the basis of their anatomical connection patterns. The two subregions were found to have distinct connections with parietal and prefrontal areas. The boundary between the subregions, as determined by tractography, co-localised consistently relative to local sulcal landmarks and to functionally-defined areas identified previously by fMRI studies.
The novel findings shed new light on the structure and function of an important area in the human brain. They also add to the evidence that diffusion-weighted imaging tractography in human volunteers is a valid and powerful approach that can replace certain animal studies in neuroscience.
Reference: Tomassini V et al (2007). Diffusion-weighted imaging tractography-based parcellation of the human lateral premotor cortex identifies dorsal and ventral subregions with anatomical and functional specializations. J Neurosci 27:10259-10269.
Read more about this Dr Hadwen Trust-funded research project here